Many different chamber lock arrangements are used to transport material through sealed pressure chambers. For example, a dewatering machine having a pressured vessel for treating filter cake resulting from, for example, metal-ore concentrates, requires a decompression chamber to allow the filter cake to pass through an area of atmospheric pressure before release from the system. Assemblies are used comprising a receiving chamber and a storage chamber or an air cell which are hermetically separated by mechanical shutoff devices. The chamber arrangements with slide valves used until this time use two slide valve halves moving in opposite directions, which meet in the middle. These assemblies work satisfactorily only up to differential pressures of approximately 2 bars with regard to the gas consumption. At higher differential pressures high leakage losses occur as a result of insufficient capacity for sealing.